To see your map details in the manager platform please click on
a "Venues & indoor maps" section. You will see your venues list
there. All the maps defined for a particular venue will be seen
when you click on the blue square ("floor maps" column). From there
you can go into details of each map and also edit it.

Sorry, i think i might have misunderstood your point. You cannot
define any maps in the venue creation steps. You do it after you
create a venue. The "Maps" button is present in the venue details
view. You can go there by clicking on "i" icon of one venue from
the list (see my image 1 with "Venues" section from previous post).
You will see the venue details and the blue "Maps" button will be
visible on the top.